Friday Hack Chat: Electronics Design And Naming A Puppy

For one reason or another, Hackaday has an extended family of ridiculously capable contributors. One of the most illustrious is [Bil Herd], Commodore refugee, electronic engineer, medic, and all-around awesome guy. He’ll be joining us over on Hackaday.io this Friday for a Hack Chat on Electronics Design.

This Friday, we’re hosting a Hack Chat with [Bil]. If you want to talk Commodore, this is the guy. If you want to talk about PLAs and programmable digital logic, this is the guy. If you want to know how to build a system from scratch in just a few months, [Bil]’s your man. [Bil] has decades of experience and his design work was produced by the millions. You’ll rarely come across someone with as much experience, and he’ll be in our Hack Chat this Friday.

[Bil] has a long career in electronics design, beginning with fixing CB radios and televisions back when fixing TVs was still a thing. Eventually, he worked his way up the engineering ladder at Commodore Business Machines where he designed the Commodore TED machines and the amazing Commodore 128.

After surviving Commodore, [Bil] has worked at a trauma center in Camden, NJ, flown with medics in the Army, and eventually came over to Hackaday where he produces videos from subjects ranging from direct digital synthesis, programmable logic, active filters, and how CMOS actually works. Basically, if it involves electronics, [Bil] knows what’s up.

Oh, as an added bonus, we get to name a puppy this week. [Bil] got a new puppy and it needs a name. Send in your suggestions!

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This hack chat will take place at noon Pacific time on Friday, June 16th. Confused about where and when ‘noon’ is? Here’s a time and date converter!

Log into Hackaday.io, visit that page, and look for the ‘Join this Project’ Button. Once you’re part of the project, the button will change to ‘Team Messaging’, which takes you directly to the Hack Chat.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about

Bil Herd Asks OBD “How Fast am I Going?”

Whenever I end up with a new vehicle I ultimately end up sticking in a new GPS/Receiver combination for better sound quality and a better GPS.

I am quite at home tearing into a dashboard as I was licensed to install CB radios in my teens as well as being the local go-to guy for 8-track stereo upgrades in the 70’s. I have spent a portion of my life laying upside down in a puddle on the car floor peering up into the mess of wires and brackets trying to keep things from dropping on my face. If you remember my post on my Datsun 280ZXT, I laid in that same position while welding in a clutch pedal bracket while getting very little welding slag on my face. I did make a note that the next time I convert a car from an automatic to a manual to do so while things are still disassembled.image15

Swapping out a factory radio usually involves choosing whether to hack into the existing factory wiring wire-by-wire, or my preference, getting a cable harness that mates with the factory plug and making an adapter out of it by splicing it to the connector that comes with the new radio.

Usually I still have to hunt down a few signals such as reverse indicator, parking brake indicator, vehicle speed sensor and the like. In my last vehicle the Vehicle Speed Sensor (VSS) wire was supposed to be in the factory harness, but driving experience showed it must not be as the GPS would show me driving 30 feet to the right of the highway. That and the calibration screen on the GPS verified that it was not receiving speed pulses.

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Computers For The Masses, Not The Classes

Retro is new again, and everywhere you look you’ll find films, documentaries, and TV shows cashing in on the nostalgia of their target audience. There is one inaccuracy you’ll find with this these shows: Apple computers are everywhere. This isn’t a historical truth – Commodore was everywhere, the C64 was the computer the nerds actually used, and to this day, the Commodore 64 is still the best-selling computer in history.

Commodore is gone, replaced with a superfund site, but the people who made the best computers in history are still around. At the 2016 Hackaday SuperConference, Bil Herd gave a talk on the second act of Commodore’s three-act tragedy. Bil is a frequent contributor around these parts, and as always he illuminates the 1980s far better than Halt and Catch Fire ever could.

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Compiling a $22 Logic Analyzer

On my way to this year’s Hackaday SuperConference I saw an article on EE Times about someone taking the $22 Lattice iCEstick and turning it into a logic analyzer complete with a Python app to display the waveforms. This jumped out as pretty cool to me given that there really isn’t a ton of RAM on the stick, basically none that isn’t contained in the FPGA itself.

[Jenny List] has also written about the this application as created by [Kevin Hubbard] of Black Mesa Labs and [Al Williams] has a great set of posts about using this same $22 evaluation board doing ground up Verilog design using open source tools. Even if you don’t end up using the stick as a logic analyzer over the long haul, it’ll be very easy to find many other projects where you can recompile to invent a new purpose for it.

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When Difference Matters: Differential Signaling

We have talked about a whole slew of logic and interconnect technologies including TTL, CMOS and assorted low voltage versions. All of these technologies have in common the fact that they are single-ended, i.e. the signal is measured as a “high” or “low” level above ground.

This is great for simple uses. But when you start talking about speed, distance, or both, the single ended solutions don’t look so good. To step in and carry the torch we have Differential Signalling. This is the “DS” in LVDS, just one of the common standards throughout industry. Let’s take a look at how differential signaling is different from single ended, and what that means for engineers and for users.

Single Ended

Collectively, standards like TTL, CMOS, and LVTTL are known as Single Ended technologies and they have in common some undesirable attributes, namely that ground noise directly affects the noise margin (the budget for how much noise is tolerable) as well as any induced noise measured to ground directly adds to the overall noise as well.

By making the voltage swing to greater voltages we can make the noise look smaller in proportion but at the expense of speed as it takes more time to make larger voltage swings, especially with the kind of capacitance and inductance we sometimes see.

Differential

diff4

Enter Differential Signaling where we use two conductor instead of one. A differential transmitter produces an inverted version of the signal and a non-inverted version and we measure the desired signal strictly between the two instead of to ground. Now ground noise doesn’t count (mostly) and noise induced onto both signal lines gets canceled as we only amplify the difference between the two, we do not amplify anything that is in common such as the noise.

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Blacksmith Forge Made From the Bathroom Sink

The sweltering heat had finally moved on and Giant Tick season was coming to a close (not kidding, they are HUGE here), when I decided to fire up my hacked together blacksmith forge made out of an old bathroom sink and aquarium stand.

In the age-old formula I needed to supply an air source to a fuel to create enough heat to make iron malleable. I got the idea that this particular bathroom sink might be a good candidate for a fire bowl after I banged my shin with it and then cursed at it. It was clearly made of cast iron and as proof it was clearly unfazed by my tirade of words which I hope my son has learned from the Internet and not from listening to me remodel the bathroom.

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From Gates to FPGA’s – Part 1: Basic Logic

It’s time to do a series on logic including things such as programmable logic, state machines, and the lesser known demons such as switching hazards. It is best to start at the beginning — but even experts will enjoy this refresher and might even learn a trick or two. I’ll start with logic symbols, alternate symbols, small Boolean truth tables and some oddball things that we can do with basic logic. The narrative version is found in the video, with a full reference laid out in the rest of this post.

Invert

1The most simple piece of logic is inversion; making a high change to low or a low change to high. Shown are a couple of ways to write an inversion including the ubiquitous “bubble” that we can apply almost anywhere to imply an inversion or a “True Low”. If it was a one it is now a zero, where it was a low it is now a high, and where it was true it is now untrue.

AND

2Moving on to the AND gate we see a simple truth table, also known as a Boolean Table, where it describes the function of “A AND B”. This is also our first opportunity to see the application of an alternate symbol. In this case a “low OR a low yields a low”

NAND

3Most if not all of the standard logic blocks come in an inverted form also such as the NAND gate shown here. The ability to invert logic functions is so useful in real life that I probably used at least three times the number of NAND gates as regular AND gates when doing medium or larger system design. The useful inversion can occur as spares or in line with the logic.

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